RESULTS
A total of 295 patients with influenza and 133 with SARS-CoV2 infection were included, of whom 52% and 55% were male, respectively. The median age was 3.7 years (IQR 1.4-7.7) for influenza and 5.3 years (IRQ 1.1-11.2) for SARS-CoV2. See table 1 and table S1 for the comparison between the two groups overall and by age group.
Comorbidities were frequent in both groups, but they were more common in patients with influenza (96.6% vs 82.7%, p <0.001). Cancer, immunodeficiency states, and heart disease were the most common comorbidities in both groups. Chronic pulmonary disease and congenital malformations were more common among children hospitalized with influenza.
Twenty-two percent of patients with SARS-CoV2 had no symptoms attributable to the infection, while only 2 patients with influenza had subclinical infection. When comparing different age groups, infants were more likely to have asymptomatic SARS-CoV2 infection (48.3% versus 16.7% among children 1 to 9 years old, and 13.6% among those 10 years of age and older, p=0.002 by Fisher´s exact test).
Among symptomatic children, fever and cough were the most common clinical manifestations in both groups, but cough was more than twice as common in patients with influenza (75.8% vs 30.1%, p<0.001). Rhinorrhea was present in more than half of children with influenza but was infrequent in those with Covid-19 (53.6 vs 5.8%, p<0.001). On the contrary, vomiting (29.1 vs 14.3%, p 0.002) and oxygen saturation <92% at hospital admission (40.8% vs 29.3%, p=0.04) occurred more commonly in children with SARS-CoV2 infection, but this difference was only observed among those 10 years and older when age subgroups were analyzed.
Admission to the intensive care unit was more common in patients with Covid-19, but the need for invasive mechanical ventilation was similar between groups (see table 2). Overall, 6.4% percent of patients with influenza and 7.5% percent of patients with SARS-CoV2 infection died. When considering different age groups, a fatal outcome occurred in 12.7% of infants, 4.3% of children 1 to 9 years old and 7.7% of those 10 years and older with influenza (p=0.08 for the difference between age groups). The rate was 10.3%, 6.7% and 6.8% in the same age groups among patients with SARS-CoV2 infection (p=0.83 for the difference between age groups).
In-hospital mortality among symptomatic patients was similar between groups in the multivariate analysis, with an odds ratio of death of 1.87 (0.78-4.45, p=0.16) among patients with Covid-19 as compared to those with influenza after adjusting for age group (<1, 1-9,> 10 years), pulmonary disease and malignant neoplasia (See table 3 and Table S2). Age 1 to 9 years was associated with lower odds of death (OR 0.27, 95% CI 0.19-0.75, p=0.01) in the logistic regression model for the whole population, while a diagnosis of cancer conveyed higher odds of in-hospital mortality (OR 2.72, 95% CI 1.06-6.95, p=0.04).
The same was true for the need for invasive mechanical ventilation, with an odds ratio of 0.86 (0.49-1.51) among patients with Covid-19 as compared to those with symptomatic influenza, after accounting for age group, pulmonary disease, and immunodeficiency (See table S3).